Steam-engine.



J. 1). MAQLAGHLAN. STEAM ENGINE.

APPLICATION FILED JAN. 28. 1907.

- PATENTED NOV. 5, 1907.

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No. 870,375. PATENTED NOV. 5, 1907.

J. D. MAQLAUHLAN. v

STEAM ENGINE.

APPLICATION FILED JAN. 28. 19.07.

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No. 870,375. PATENTED NOV. 5; 1907,

J. D. MAGLAGHLAN.

STEAM ENGINE. APPLICATION FILED J-AN. 28.1907.

3 SHEETS- SHEET 3.

WITNESSES ATTORNEY YHE Nonms psrsns co.

UNITED STATES PATENT OFFIQEL JOHN D. MACLAOHLANLOF DETROIT, MICHIGAN, ASSIGNOR TO DETROIT STEAM ENGINE I COMPANY OF DETROIT, MICHIGAN.

STEAM-ENGINE.

Specification of Letters Patent.

Patented Nov. 5, 1907.

Application filed January 28,1907. Serial No. 854L467.

This invention relates to valve mechanisms for steam engines and more particularly to that class of compound engines which can be quickly transformed from compound to simple by converting the high pressure cylinders into mere receivers or by-passes through which the steam flows on its Way to the low-pressure cylinders, where it does its work. Engines of this class are usually made up of two or more compound engines, each consisting of a highand a low-pressure cylinder arranged fore-and-aft on the same crank shaft. Oompound engines so arranged are usually converted into simple engines by manipulating the inlet valves so as a to permit the steam to flow through the high pressure cylinders without doing effective work in themthe effective work being accomplished in the low pressure cylinders only. When two compound engines are so connected, it sometimes occurs when shutting down the engine, that the cranks stop in such a position that their turning efforts counterbalance. A balanced position in the case of two such compound engines is shown when the low pressure cranks occupy the position of an 3 inverted V. In this position, one of the low pressure pistons being on its up-stroke and therefore exhausting, has no steam pressure on it. The other low pressure piston, being at about the point of cut-off, and near its lower dead point, exerts practically no effective turning effort on the shaft. The two high pressure pistons are balanced, both being under full steam pressure. In such event, it is impossible to start the engine by the admission of live steam simultaneously to both high pressure cylinders.

The object of my invention is to provide means for automatically shutting off steam from one high pressure piston when the balanced position is reached, thereby permitting the other high pressure piston to exert its full efiort.

In the accompanying drawings, Figure 1 is a vertical sectional view of an engine equipped with my invention, Fig. 2 is a top plan view thereof, the high pressure inlet valves being projected in section. Fig. 3 is a side view, broken away in part. Fig. 4 is a diagrammatic view showing the positions of the cranks when in the balanced position. Figs. 5 and 6 are details of the cams controlling the high pressure inlet valves. Figs. 7, 9 and 11 are side views of a pair of cams for controlling the high pressure inlet valves, the cams being partially rotated in the different views to bring out their contour more clearly. Figs. 8 and 10 are side views of one pair of cams for admitting steam to the low pressure cylinders, and Figs. 12 and 13 are end views of the high pressure inlet cam.

A indicates the high pressure and B the low pressure cylinders, mounted on a crank base (M).

G indicates the high pressure pistons connected by rods (E) with the crank shaft (G).

H indicates the low pressure pistons connected by rods (F) with the shaft (G).

.T indicates ports for admitting live steam to the high pressure cylinders, such ports being'controlled by the valves (K) having valve stems (L) operated by means within the crank base (M), hereinafter set forth, the lowerends of the valve stems being preferably equipped with hardened steel balls (N). The inlets (J) (J) may be connected by a pipe (O) communicating with a source of steam.

P indicates valve casings located in the passage between the high and low pressure cylinders. In each casing is located a valve (not shown) adapted to be actuated suitable cams (R) shown in Figs. 8 and 10.

The cams are carried on a suitable revoluble cam shaft,not shown, as it forms no part of the present invention.

S indicates the valve casings in which are located the low pressure exhaust valves,not shown, the stems of which are actuated by cams similar in shape to those shown in Figs. 8 and 10.

' The crank shaft (G) is mounted in suitable bearings in the crank base (M) and is provided with a gear (F) with which an intermediate gear (U) meshes, said intermediate gear adapted to mesh with a. driven gear, not shown, on a cam shaft (V), which shaft is longitudinally adjustable in bearings (t) in the crank base. This cam shaft is provided intermediate its length with the cams (l) (1), shown in Figs. 7, 9 and 11, such cams having the oppositely extending inclines (2) (2) formed thereon between which is the neutral point or cylin drical belt (3). The ends of the cams are eccentric in section, as shown in Figs. 12 and 13. The lower ends (N) of the valve stems (L) are engaged by the cams, whereby the valves (K) are operated to admit steam to the high pressure cylinders (A) (A). Shifting the cams and cam shaft (V) longitudinally operates to vary the length of time the valves are held open. Other cams operate the valves in valve casings (P) and (S). It will therefore be seen that the inlet valves (K) can, by suitably formed cams, be held open a longer or shorter time, as desired.

The ends (4) of the inlet cams have heretofore been made circular and of sufficient diameter to hold the valves (K) open throughout one or more cycles of movement of the pistons (O), the result being to convert a compound into a simple engine by admitting a continuous uninterrupted supply of steam to the high pressure cylinder, and allowing it to flow through the high into the low. In passing from the high to the low, it goes through the valves (1?) (P) in the usual manner. It has ,been found in practice, however, that the pistons (F) of the low pressure cylinders may sometimes halt at the position illustrated in the diagram, Fig. 4, wherein the cranks (d) (d), represented by full and dotted lines,'respectively, assume the position of an inverted (V). With the cranks in this position, if live steam is admitted simultaneously to both high pressure cylinders, the pressure will balance and no movement will be imparted to the shaft (G)in other words, the engine will not start. To remedy this defect and enable the engine to start from any position, I provide on the cams (1), that control inlet valves (J),eccentric ends (4) having a low spot or short radius as indicated at (5). The short radii are arranged on the cam so that the low spot (5) on one of the high pressure inlet cams permits its high pressure inlet valve to close for an instant when the cranks are in the balanced positions indicated in Fig. 4.

When a double compound engine, such as illustrated, is run as a simple engine, in the manner above described, the continuous flow of steam to one of the high pressure cylinders is, by my improvement, interrupted for a short space of time, while steam has free access to the other high pressure, destroying the balance.

Should the engine stop in the balanced position indicated by Fig. 4, the end of one of the yalve rods (L) will rest in the low spot (5) of the eccentric end of its cam (1), thereby shutting off steam from one high pressure cylinder. The steam, however, has free access to the other high pressure cylinder, so that the pressure on one side of the crank shaft (G) overcomes that on the opposite side of the shaft, thereby rotating the shaft and starting the engine.

While I have shown and described this invention as applied to a single acting, it is to be understood that this improvement is adapted also for use with a double acting engine.

Having thus fully disclosed my invention, what I claim as new is 1. The combination in an engine comprising a plurality of high and low pressure cylinders arranged in pairs, and inlet valves communicatingwith the high pressure cylinders, of means for holding said valves open throughout one or more cycles, said means adapted to temporarily seat one of the inlet valves when the cranks are in balanced positions.

2. The combination in an engine comprising a pinrality of high and low pressure cylinders arranged in pairs, and inlet valves communicating with the high pressure cylinders, of cams for holding said valves open throughout one or more cycles, said cams adapted to temporarily seat one of the inlet valves when the cranks are in balanced positions.

The combination in an engine comprising a plurality of high and low pressure cylinders arranged in pairs, inlet valves communicating with the high pressure cylinders, a shaft extending in alinement with the inlet valves and cams on the shaft for operating the valves, the outer ends of the cams each being concentric with the shaft and having a depressed contour forming a low spot adapted to permit one of the inlet valves to temporarily seat when the cranks are in balanced positions.

l. The combination in an engine comprising a plurality of high and low pressure cylinders arranged in pairs, inlet valves communicating with the high pressure cylinders, a shaft extending in alinement with the valves, cams on the shafts, the cams comprising body portions concentric with the shaft. and inclined spiral ribs projecting from the peripheries of the body portions, the inclines extending in opposite directions from points near the transverse center of the body portion, the ribs gradually increasing in width from their inner-ends to their outer ends the outer ends of the ribs nearly encircling the body portion so as to form a depression.

In testimony whereof, I aflix signature in presence of two Witnesses.

JOHN D. MACLACHLAN.

Witnesses GEORGE W. GOLDEN, JAMns WIn'r'ry. 

